A third international workshop on natural killer cells is proposed for July 3-6, 1986. The workshop will be a closed meeting of 40-50 experts in this area, and will be held at the Donald Gordon Centre, Queen's University, Kingston, Ontario. The Center is a former private residence which has been renovated as a conference center. It is completely self contained, with full accommodation, dining and meeting facilities. The workshop will be a satellite meeting of the 6th International Congress of Immunology, Toronto July 6-11. The workshop will be divided into eight sessions, with two evenings being set aside for small group discussion. The sessions will deal with: expression of T cell genes by NK cells, the lineage of NK cells, the mode of action of NK cytotoxicity, NK target structures and factors affecting susceptibility of targets to lysis by NK cells, non-cytolytic functions of NK cells, the role of NK cells in antimicrobial defence, the regulation of NK function by biological response modifiers, and anti-tumor surveillance and the prevention of metastatic disease by NK cells. The general format will be similar to that of the first two NK workshops, which were considered to be extremely useful and informative. Each session will be chaired by an expert in the field and will be organized so as to generate maximum discussion with minimum formal presentation. The meeting as a whole has been planned so as to cover many aspects of the field of NK cells, with the aim being that delegates will present new data relevant to the session, with the ensuing discussion being devoted to the resolving of conflicts between different laboratories and to determing what is fact and what is still unproven from our current data base. We know from past workshops that a group of this size is optimun for the frank exchange of ideas and constructive criticism. The inclusion of a somewhat broad range of topics is deliberate. Again, the previous NK workshops demonstrated that many individuals benefitted from, and contributed in major ways to, sessions peripheral to their own field of specialization, primarily because issues of methodology, NK lineage, mechanism of action and biological relevance are of interest to all workers in this area. The literature in the NK field is still increasing at an exponential rate - it is essential that interested investigators meet together to put this information in perspective.